Effect of monoclonal antibody therapy on the endogenous SARS-CoV-2 antibody response

Monoclonal antibody treatment of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection has been widely implemented. Effects of treatment on the endogenous primary humoral response to the virus are unknown. A retrospective cohort study performed at a Veterans Health Administration medical center compared serologic responses of treated and untreated COVID-19 patients at high risk for severe outcomes. Three anti-viral spike protein IgG monoclonal treatments were used during the study period, 1) bamlanivimab, 2) casirivimab with imdevimab, and 3) bamlanivimab with etesevimab. Data were analyzed at acute (0–9 days), seroconversion (10–19 days), and maximum antibody (20–39 days) stages. SARS-Cov-2 infection induced a dynamic primary humoral response with anti-spike IgM and anti-nucleocapsid IgG seroconversion occurring after 9 days with maximum serologic indices achieved by 20–39 days. All monoclonal antibody treatments suppressed the endogenous anti-spike IgM response by 85–90% with minor effect on the anti-nucleocapsid response. Thus, passive immunization therapy may cause immunologic interference.